Merge pull request #2473 from Automattic/fix/mobile-menu-flash

#2382 swaped the z-index of the menu buttons to avoid flash

seedlet/assets/css/ie.css

@@ -4265,13 +4265,13 @@ nav a {
 .primary-navigation .button.open,
 .woo-navigation .button.open {
 	display: flex;
-	z-index: 499;
 }
 
 .menu-button-container .button.close,
 .primary-navigation .button.close,
 .woo-navigation .button.close {
 	display: none;
+	z-index: 501;
 }
 
 .menu-button-container .button#woo-open-menu {

seedlet/assets/sass/components/header/_primary-navigation.scss

@@ -35,10 +35,10 @@
 
 		&.open {
 			display: flex;
-			z-index: 499;
 		}
 		&.close {
 			display: none;
+			z-index: 501;
 		}
 
 		&#woo-open-menu {

seedlet/style-rtl.css

@@ -2918,13 +2918,13 @@ nav a {
 .primary-navigation .button.open,
 .woo-navigation .button.open {
 	display: flex;
-	z-index: 499;
 }
 
 .menu-button-container .button.close,
 .primary-navigation .button.close,
 .woo-navigation .button.close {
 	display: none;
+	z-index: 501;
 }
 
 .menu-button-container .button#woo-open-menu,

seedlet/style.css

@@ -2943,13 +2943,13 @@ nav a {
 .primary-navigation .button.open,
 .woo-navigation .button.open {
 	display: flex;
-	z-index: 499;
 }
 
 .menu-button-container .button.close,
 .primary-navigation .button.close,
 .woo-navigation .button.close {
 	display: none;
+	z-index: 501;
 }
 
 .menu-button-container .button#woo-open-menu,